Digital repositories are emerging to meet the needs of scholars and researchers who rely heavily upon digital data and content in their research. Maintaining digital resources over time is necessary to permit longitudinal or time lapse studies, and to preserve researchers' ability to support, and others to evaluate, their findings. There is a need for “long-lived” collections of digital content and data. Some repositories specialize in data for particular fields or disciplines. Others aggregate digital content on a variety of subjects.

TRAC [2]- Trusted Repository Archiving Checklist (TRAC) contains metrics that help in judging the repository in the areas of Administration and Policy, Object Handling and Technology. It was published by CRL in 2007.

I[5]SO 16363[3], or TDR[4] - is an ISO standard as of February of 2012. It is a revision of the TRAC Checklist. Many of the changes were structural, and it continues to address the same core areas of repository activity. TDR is a free, unofficial version published by the Consultative Committee for Space Data Systems (CCSDS)[6] who sponsors the working groups for TDR, OAIS and other relevant digital repository standards.

Ten Principles[7] - A list of ten core principles digital repositories must exhibit in order to be trusted.

Other tools[8] - CRL provides access to other tools for evaluating digital repositories.